## Fundamental Units involved in Energy Measurements

Power = Energy/Time

SI unit of power is watt and that of energy is joule (1 watt = 1 joule/sec)

The electricity is usually expressed in terms of power as Megawatts (MW)

1 MW = 1,000,000 W = 1,000,000 J/s

The electricity is also commonly expressed in terms of energy as kilowatt-hour

1 kilowatt-hour is the energy when 1 kilowatt (1000 W) power is produced for 1 hour

i.e., 1 kWH = 1000 W x 3600 s = 3,600,000 J = 3600 KJ

Energy is also commonly expressed as calorie. A calorie is the amount of energy required to raise the temperature of 1 gm of water by 1 oC

1 calorie = 4.184 joules

Another commonly used unit is British thermal unit (Btu). A Btu is the amount of energy required to raise the temperature of 1 pound of water by 1 oF

1 Btu = 1055.06 joules

100,000 Btu = 1 therm

Approximate Cost: $0.15 per kwh (May change significantly based on location and season of use).

SI unit of power is watt and that of energy is joule (1 watt = 1 joule/sec)

The electricity is usually expressed in terms of power as Megawatts (MW)

1 MW = 1,000,000 W = 1,000,000 J/s

The electricity is also commonly expressed in terms of energy as kilowatt-hour

1 kilowatt-hour is the energy when 1 kilowatt (1000 W) power is produced for 1 hour

i.e., 1 kWH = 1000 W x 3600 s = 3,600,000 J = 3600 KJ

Energy is also commonly expressed as calorie. A calorie is the amount of energy required to raise the temperature of 1 gm of water by 1 oC

1 calorie = 4.184 joules

Another commonly used unit is British thermal unit (Btu). A Btu is the amount of energy required to raise the temperature of 1 pound of water by 1 oF

1 Btu = 1055.06 joules

100,000 Btu = 1 therm

Approximate Cost: $0.15 per kwh (May change significantly based on location and season of use).

Appliance |
watt |
Hours/Day | kwh |

40-49 in Plasma |
400 | 4 | 1.6 |

Dishwasher | 1200 | 1 | 1.2 |

Refrigerator | 500 | 10 | 5.0 |

Dryer | 5000 | 0.5 | 2.5 |

Washer | 500 | 0.5 | 0.25 |

Water Heater |
4500 | 2.5 | 11.25 |

Computer | 300 | 8 | 2.4 |

Portable Heater |
1500 | 4 | 6.0 |